The invention relates to a gas-sensor arrangement for measuring a target-gas concentration with a radiation emitter, by means of which radiant energy can be projected through a space containing the target gas, a radiation receiver, by means of which radiant energy projected by the radiation emitter can be detected, a filter that is assigned to the radiation receiver and that is permeable to radiation of a wavelength range corresponding to the target gas, and a controller that is connected to the radiation receiver and by means of which the target-gas concentration can be calculated on the basis of a detector signal applied by the radiation receiver to the controller.
Such gas-sensor arrangements are increasingly being used to monitor air quality, wherein in particular the quality of outdoor air and/or the quality of air present in internal spaces, in particular also passenger compartments of vehicles, is monitored.
For the monitoring of air quality in internal spaces, it should be ensured that any deterioration in this air quality can be responded to with suitable measures.
In the area of vehicles, use has for some time been made of gas-sensor arrangements suitable for this purpose, which include metal oxide sensors (MOS), by means of which the air is monitored for the presence of VOC (volatile organic compounds). In the case of excessively high concentrations of these VOC in the air present in the passenger compartment of the vehicle, it is possible by using such gas-sensor arrangements for the vehicle ventilation system to be switched on automatically in order to provide an exchange of air.
Use is increasingly being made of air-conditioning systems in motor vehicles, wherein carbon dioxide (CO2) is used as a refrigerant. Since carbon dioxide, when its concentration increases in the passenger compartment air, can lead to tiredness and sleepiness on the part of the vehicle driver, gas-sensor arrangements are also used to monitor leakages in the air-conditioning system. In these cases, the gas-sensor arrangement constituted as a CO2 sensor arrangement is intended, in the case inadmissible CO2 concentrations in the passenger compartment air, to trigger an alarm or to act on a control device of a vehicle ventilation system with the aim of eliminating the hazard due to an excessively high CO2 content in the passenger compartment air. This could be brought about for example by increasing the air throughput in the vehicle passenger compartment, as a result of which the CO2 concentration inside the vehicle passenger compartment is reduced.
A method for monitoring the air quality in a vehicle passenger compartment is known from DE 10 2004 024 2841 [US 2005/0038582], wherein a hazard prevention for living creatures that are present in the passenger compartment of a parked car is intended to be provided by a gas-sensor arrangement suitable for detecting CO2. Here, the passenger compartment temperature is also monitored apart from the CO2 content of the passenger compartment air. If, in the presence of a comparatively high passenger compartment temperature, a predefined CO2 increase gradient is detected, it is assumed that a living creature, for example a child or a domestic animal, is present in the passenger compartment of a motor vehicle. Here, the CO2 increase gradient is characteristic of the fact that breathing is occurring in the passenger compartment of the motor vehicle.